[LargeFormat] Double Protar Lens

[Ken Strauss]

You frequently refer to Kingslake's book. I have his "Lenses in =
Photography"
but he published many others; which do you find most useful?=20

-----Original Message-----
From: largeformat-admin@f32.net [mailto:largeformat-admin@f32.net] On =
Behalf
Of Richard Knoppow
Sent: September 5, 2003 17:22
To: largeformat@f32.net
Subject: Re: [LargeFormat] Double Protar Lens


----- Original Message -----=20
From: "Clive Warren" <Clive.Warren@megacycle.co.uk>
To: <largeformat@f32.net>
Sent: Thursday, September 04, 2003 3:38 PM
Subject: Re: [LargeFormat] Double Protar Lens


> At 17:31 04/09/2003 -0400, LNphoto wrote:
> >A pair of 16 1/16" make for a 9 1/4" focal length that
covers 6x8 wide
> >open and 8x10 at "smaller stops" usually f22
> >
> >I gotta check other sources on the lettered sets.
> >
> >the 16" Was part of the D set and in it's "normal" mount
is probably the
> >same as the 18" cell.   The pair of 11" lenses are
probably in a smaller
> >mount than the 16.
> >
> >So the 11" cells are US system.  That's unusual, at least
here in the
> >States.   For the most part US system had been cast aside
like a DAT tape
> >or a laser disc by WWI.  Maybe it hung on later over
there.
> >
> >Les
>
> Les,
>
> Thanks for that - a bit longer combined FL than
anticipated. Not too much
> in the way of movement on 8x10 then... at least it covers.
It may end up
> being used on 5x7. Will keep my eyes open for the longest
D set focal
> length cell.
>
> The 11" cells are Bausch and Lomb so originate in the USA.
From the 1958
> edition Focal Press Encyclopedia, The US system was
proposed in 1881 by the
> Royal Photographic Society and was not much used in
Britain or 'on the
> continent' <grin>  '......but it was used for some time in
America,
> particularly on earlier Kodak cameras'. p.349 Vol. 1.
>
> If we suppose that the lenses were made from 1895 (the
patent date) then
> quite a few would have been made by 1914 as they were one
of the best
> lenses available until around the early 1920's.
>
> So it seems that we (UK) didn't always adopt new systems
after you guys had
> already rejected them and moved onto something better :-)
>
> Cheers,
>             Clive
>
>
   B&L seems to have been the main user of the US system of
stops. It is found mainly on B&L Rapid-Rectilinear lenses
and can be found on those made up to the early 1930s!
   Shutters for some Protar sets are calibrated in mm rather
than f/stops. You can tell these easily because the numbers
get smaller as the aperture gets smaller.
  Without digging out Kingslake's little book on Rochester,
N.Y. photographic companies I can't be sure of the date of
the agreement between B&L and Zeiss but by memory it
predates 1900. Its possible some early Protars were
calibrated in US stops.
  BTW, a number of stop systems were proposed in the late
19th century, mainly in an attempt to show some direct
relationship to either light gathering power or to exposure
time. None was very successful. I think the US system was
the only one to get much use. Zeiss had at least two systems
but they were used almost exclusively on lenses sold in
Germany.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com


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